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Changing tires on evolution's bumpy meandering road

Post of the Month: December 2008


Subject:    | Iain confuses Behe's test for IC with a claim about historical
Date:       | 18 Dec 2008
Message-ID: |

Iain Inkster wrote:
>> Evolutionary theory does not postulate that modern structures
>> are derived from functionally incomplete versions of modern
>> structures.

Toni Pagano wrote:
> This has been the mantra since 1996 when Behe identified at
> least two real world "irreducibly complex" structures/systems
> which refute neoDarwinism as the universal engine of
> biological novelty and diversity.

> Random mutations and natural selection can only act on
> EXISTING function regardless of whether that function is
> rudimentary or modern. And purely naturalistic processes are
> by necessity gradualistic and linear.

Steven L. replies:
Evolutionary processes are hardly linear.

In the history of life on Earth, the power of flight has been gained and lost numerous times, the power of vision has been gained and lost numerous times, fish evolved into tetrapods which colonized the land and then cetacean mammals returned to the water, etc. Now why did that happen? It happened because the environment, against which the organism had to adapt, was constantly changing. Sometimes sight is advantageous, sometimes it isn't.

And because of this forward-backward movement, it's easy to lose sight of how the end product was attained.

Every time you change the tire on your car, you have to deal with this.

If you could only "act on the existing functions" of the car, you would have to change the tire while all four existing tires of the car rest on the ground, which would be impossible. Instead, you add a *temporary* function (the jack), jack up one wheel, change the tire on that wheel, lower that wheel back to the ground, and then remove that jack function again. At all times you were acting on existing function.

But what you did was a *nonlinear* process--you introduced a temporary element (the jack) only to get rid of it again at the end.

But if you didn't know that's how tires are changed, and you looked only at the finished end product (a car with four fully-inflated tires), you would conclude that it's impossible to change a car's flat tire--you can't get the tire under the wheel rim as long as that wheel is sitting on the ground.

In engineering, many things work this way: Skyscrapers are erected with temporary scaffolding that is removed before the building is open for business. Highway overpasses are erected with hydraulic rams that hold them up until the overpass is built and can stay up on its own, after which the hydraulic rams are removed.

With species that are constantly gaining and losing function in order to adapt to new environments, it's easy to lose track of the "temporary scaffolding" that got a species to where it is. That "temporary scaffolding" is an ancestor species that no longer needs that highly specialized function.

> This means that the neoDarwiniam evolutionary algorithm can,
> generally speaking, only move up a particular fitness peak of
> existing function, it cannot jump from that peak to another.

The metric of "fitness" doesn't stay constant throughout this migration.

Unlike many state-space optimization problems in system space (which is what I think you're referring to), "fitness" is simply relative to whatever the environment is at a given point in time--and that's always changing. Let's say the evolutionary algorithm achieves a local optimum relative to that. Tomorrow, the environment changes, and now that local optimum is no longer valid. The search begins again, and a new local optimum may be found (if the environment doesn't change again in the meantime!)

In sum, the evolutionary algorithm is constantly "chasing" the fitness forcing function, as it is itself being forced by the changing environment. And a global optimum may never be found throughout all of this.

> It certainly does postulate that the neoDarwinian mechanism
> can only act on EXISTING FUNCTION.

See above. What you neglect is that some functions that get added, are simply temporary "helpers" to some other end--like the hydraulic rams and scaffolding. They come and they go before you notice the end product.

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